Caching contents close to end-users can improve the network performance, while causing the problem of guaranteeing consistency. Specifically, solutions are classified into validation and invalidation, the latter of which can provide strong cache consistency strictly required in some scenarios. To date, little work on the analysis of cache invalidation has been covered. In this work, by using conditional probability to characterize the interactive relationship between existence and validity, we develop an analytical model that evaluates the performance (hit probability and server load) of four different invalidation schemes with LRU replacement under arbitrary invalidation frequency distribution. The model allows us to theoretically identify some key parameters that affect our metrics of interest and gain some common insights on parameter settings to balance the performance of cache invalidation. Compared with other cache invalidation models, our model can achieve higher accuracy in predicting the cache hit probability. We also conduct extensive simulations that demonstrate the achievable performance of our model.

Caching content in routers is the most significant feature of Named Data Networking (NDN) and therefore the cache performance is increasingly being concerned for NDN deployment. The default cache policy of NDN is Leave Copy Everywhere (LCE) that leaves the copies in each node the data packet passed, and most of the copies will not be requested again, which leads to the waste of cache resources. The Betweenness Strategy caches data in the node with the maximal betweenness value, which causes a high replacement rate. Considering the betweenness of nodes and the popularity of content, as well as the filter effect of cache, we propose Betweenness and Edge Popularity strategy (BEP) which caches the most popular content in the most important nodes. We also conduct comprehensive simulations based on ndnSIM. By evaluating BEP and other cache replication strategies on a virtual topology, it is indicated that BEP can achieve higher performance in terms of the cache hit ratio, server load and average delay.